25th January 2014

Global warming continues: 2013 was fourth hottest year on record

The average combined land and ocean surface temperature for January–December 2013 was tied as the fourth warmest such period on record, at 0.62°C (1.12°F) above the 20th century average.

The latest summary of global temperature released by the National Oceanic and Atmospheric Administration (NOAA) concludes that warmer-than-average temperatures affected the vast majority of the globe during 2013. Record warmth was observed across much of southern and western Australia, southwestern Ethiopia, eastern Tanzania, parts of central Asia around Kazakhstan and Uzbekistan, a large section of the southwestern Pacific Ocean, along with regions of the Arctic, central Pacific, and central Indian Oceans.

Temperatures were cooler-than-average across the central United States – a region that saw record warmth in 2012 – along with small sections of the eastern Pacific Ocean and the Southern Ocean off the tip of South America. No record coldest regions were observed for the January–December 2013 period, as shown in the map below.

Globally, 2010 remains the hottest year recorded by NOAA at 0.66°C (1.2°F) above the 20th century average, with 2005 and 1998 in second and third place, respectively. Including 2013, all 13 years of the 21st century (2001-2013) rank among the 15 warmest in the 134-year observational record. Viewed over a longer timescale, the trend is even more obvious. Last year's high temperatures occurred even without El Niño, suggesting that a new record may soon be reached and casting doubt on recent claims of a "pause" in warming.

Despite the overwhelming evidence, the near-unanimous agreement from climate experts, and growing number of disasters affecting the world, much of the public still believes that a controversy exists in the scientific community and/or experts are distorting the truth. Gallup polls show that 40% of U.S. adults view global warming as exaggerated, with a similar number thinking natural causes are to blame.

In fact, the evidence for climate change (a term used since at least 1955) and humanity's contribution to it has become stronger than ever. Study after study confirms that human industrial activity is clearly and by far the dominant factor driving the recent changes in our atmosphere:

Credit: SkepticalScience (CC BY 3.0)

We have known since the 19th century that CO2 is a greenhouse gas – trapping heat in ways that can be demonstrated with even simple experiments. By analysing the ratio of carbon isotopes, we can easily determine what proportion is natural and what proportion is man-made. From this, we know that our carbon emissions have been absolutely colossal when measured on a geologic timescale, with changes now happening 10 times faster than any period since the Cretaceous–Paleogene extinction event of 65 million years ago. We know that the so-called Medieval warm period, while unusually warm in some regions like the North Atlantic, was much cooler than today on a global basis. We know that solar activity is not a cause of recent warming and new research indicates that climate sensitivity to CO2 input has been underestimated. We know from simple experiments that even a small increase in parts per million can have an obvious impact.

There is abundant evidence of current impacts in the form of shrinking glaciers (including the Glacier National Park), larger and more damaging wildfires, ocean acidification and deoxygenation, loss of coral reefs, fish migrations, bark beetle and other pest movements, rising sea levels, coastal erosion, extremes in flooding and drought, along with more frequent heat waves. We know that Arctic sea ice is melting 50 years ahead of earlier forecasts and that ice loss in the region is far greater than the relatively small gain in the Antarctic. We know that vast areas of carbon-absorbing forests have been cut down over the centuries and particularly during the last decade – in order to make way for our sprawling cities and their carbon-spouting automobiles – not to mention thousands of planes in the skies overhead – all of which have appeared on this planet in the blink of an eye, geologically speaking. Any supposed "benefits" to plants from extra CO2 will be offset by the negative effects from drought, weeds and higher temperatures. There are tens of millions of people around the world already being affected by this panoply of converging impacts. Recent ventures into unconventional fossil fuels are the stuff of nightmares.

We have the world's most powerful supercomputers, making trillions of calculations per second for months on end, running state-of-the-art simulations with fantastic levels of detail. Contrary to what some would claim, these models have proven remarkably successful, correctly predicting:

• That our land, atmosphere and oceans would warm.
• That the troposphere would warm and the stratosphere would cool.
• That nighttime average temperatures would increase more than daytime average temperatures.
• That winter average temperatures would increase more than summer average temperatures.
• That polar amplification would lead to greater temperature increases nearer the poles.
• That the Arctic would warm faster than the Antarctic.
• The magnitude (0.3 K) and duration (two years) of the cooling from the Mt. Pinatubo eruption.
• The amount of water vapour feedback due to ENSO.
• The response of southern ocean winds to the ozone hole.
• The expansion of the Hadley cells.
• The poleward movement of storm tracks.
• The rising of the tropopause and the effective radiating altitude.
• The clear sky super greenhouse effect from increased water vapour in the tropics.
• The near constancy of relative humidity on global average.
• That coastal upwelling of ocean water would increase.
• They performed a retrodiction for the Last Glacial Maximum sea surface temperatures, which was inconsistent with the paleo evidence, and better paleo evidence subsequently showed the models were right.

And yet, even without these computer models, there is clear evidence of climate change and our influence on it. Decades of peer-reviewed studies in the world's top scientific journals have confirmed this reality; just as they confirmed the reality of evolution, our planet's geologic history, the germ theory of disease, links between smoking and cancer, depletion of the ozone layer by CFCs, along with countless other biological, chemical and physical processes. The science can never be perfect and there will always be gaps, but today no scientific body of national or international standing disputes the fundamental points.

There are, of course, a small number of individual climate scientists who claim to be sceptical. In almost every case, however, they either have ties to fossil fuel interests, or their work has never been peer-reviewed and published in a respected journal. It is worth noting that individuals like Christopher Monckton are not climate scientists and are totally unqualified in the field. A recent documentary, The Great Global Warming Swindle has been savaged by climatologists for its cherry picking, inaccuracies and misleading claims. Many arguments continue to be made by sceptics (such as the 1970s cooling myth), but literally none stand up to scrutiny. The science behind climate change is robust and has withstood almost everything thrown at it – including the recent "Climategate", with multiple independent inquiries finding no evidence of fraud or scientific misconduct.

Given all of the above, the risks of inaction – and the obvious benefits of clean technology – how can people be so eager to embrace fossil fuels, so confident in their scepticism, and willing to take such a gamble on their children's future? Even the conservative U.S. military now takes the issue seriously and is preparing for the impacts. If climate scientists are in it for the money, they're doing it wrong.

Global warming is the biggest story of our time, a result of our explosive growth in population and technology. It will define the 21st century and possibly many centuries to come. Ignoring the evidence and casually dismissing what decades of peer-reviewed science have told us would be a mistake of truly monumental proportions.

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